This invention relates to bicycle gear shifters and more particularly to a bicycle gear shifter having a shift control member for pulling a control cable and a separate shift control member for releasing the control cable.
It is known in the art to provide a gear shifter that has separate mechanisms for pulling and releasing a control cable connected to a gear-change mechanism. Such a shifter is shown in German Utility Model Publication DE G9212927 (Jedek). This shifter includes both a first shift control member rotatable about the handlebar to pull cable and a second shift control member, a finger-operated lever, operable to release or unwind the cable. The release lever disclosed is a two-stroke or return-to-neutral device having both an actuation stroke and a reversibly-sprung return stroke. Since the release lever is linked to a takeup element through a ratchet, the takeup element is released and unwinds under the lever actuation stroke, when the rider depresses the lever, and is prevented from further unwinding under the lever return stroke, when the rider releases the lever to reengage the takeup. Since the takeup element in this device may fully unwind under the lever actuation stroke alone, the rider must carefully time his release of the lever (i.e. the lever return stroke) in order to shift to the desired gear and prevent full unwinding of the takeup. In other words, two strokes, both the actuation and return strokes of the release lever are required in order to achieve a gear change corresponding to less than a full unwinding of the takeup element.
Another bicycle shifter is disclosed in U.S. Pat. No. 5,802,923 (Hara). The Hara shifter also includes a first shift member rotatable about the handlebar for pulling a cable and a separate return-to-neutral lever for releasing the cable. The release lever disclosed in this patent is linked to a takeup element by a pair of toggling pawls forming an escapement mechanism. The toggling pawls sequentially engage the takeup element in response to operation of the release lever. Although the presence of a second pawl in the Hara shifter prevents the uncontrolled unwinding of the takeup element described above in the Jedek shifter, it introduces an undesirable two-step cable release operating sequence. Under the actuation stroke of the release lever, when the rider depresses the lever, the second pawl is toggled to engage the takeup element permitting partial unwinding of the takeup. Subsequently, under the return stroke of the lever, when the rider releases the lever, the second pawl is disengaged to permit sufficient unwinding of the takeup element to complete the desired shift. In other words, the desired full release shift occurs only through the staggered, two-stroke or two-step operation of the release lever, triggering two discrete start-stop motions of the derailleur to which the control cable is attached. The Hara shifter, therefore, embodies intermittent operation of the release lever leading to interrupted motion of the gear-change mechanism to which it is attached. Such a staggered cable release sequence is counterintuitive to the rider resulting in cumbersome and choppy shifting. Furthermore, the toggling pawls of the Hara device require greater precision to manufacture, including tighter manufacturing and assembly tolerances, resulting in higher manufacturing costs.
Another bicycle shifter having two shift control members is disclosed in U.S. Pat. No. 6,209,413 (Chang). This shifter includes both a grip rotatable about the handlebar for pulling a cable and a separate release ring also rotatable about the handlebar for releasing the control cable. The release ring of the Chang device, however, is operable to achieve multiple gear shifts for each actuation stroke or operating twist of the release ring, leading to possible inadvertent multiple release shifts when riding on rough terrain. Additionally, the release ring of this device does not return to a home or neutral position upon completion of each release shift operation. Although this type of device does permit the rider to select one or more release gear shifts per operation of the release ring, it does not permit the quick and predictable, single-gear, return-to-neutral release shifts of the present invention.
For the foregoing reasons, there is a need for a bicycle shifter having separate cable pull and cable release control mechanisms, including a release control member permitting predetermined, single gear, return-to-neutral release shifts, where the entire cable release for the single gear shift occurs under a single strokexe2x80x94actuation or returnxe2x80x94of the release control member.
The present invention is directed to a shifting device that satisfies this need. One object is to provide a bicycle shifter that pulls cable by rotating a first shift control member about the handlebar and releases cable by actuating a separate second shift control member in such a way that the rider can predictably release a single gear using a single actuation or a single release stroke of the release lever even on very rough terrain.
Another object of the invention is to provide a shifting device having a cable release control member that is conveniently and ergonomically located for easy operation by the rider be it a lever, pushbutton, or rotatable ring design. The invention likewise includes an ergonomic first control member that may include a handgrip or a finger-actuated member.
A further object of the invention is to provide a shifting device having a cable release operation that precisely releases a single gear with a single actuation or single return stroke using fewer parts, permitting larger manufacturing and assembly tolerances, and permitting compact packaging of the shifter and production at reduced costs.
Accordingly, the shifting device includes first and second shift control members, a takeup element, a holding member, and a release member. The takeup element is configured for winding and unwinding a control cable. The first control member is rotatable about a handlebar and configured to rotate the takeup to at least pull or wind the control cable onto the takeup. The second control member is a return-to-neutral member for rotating the takeup to release or unwind the cable an amount corresponding to a single gear. The holding member is rotatable with the takeup and configured to retain the takeup in select or particular angular positions. The release member is operable for releasing the holding member in response to the actuation stroke or the return stroke of the second control member for allowing the takeup to unwind the cable a sufficient amount to complete one gear shift.
In the shifting device of the present invention a release transmission may be used to communicate the motion of the second control member to the release member. The release transmission may be configured to respond to the actuation stroke or the return stroke of the second control member.
In the shifting device of this invention, the takeup element may be rotatable with or separately from the first control member. In the embodiments where the takeup is separately rotatable from the first control member, a ratcheting driving member may be used to permit unwinding of the takeup separately from the first control member. In the case of a handgrip first control member, for example, the rider may effect a cable release shift without releasing his grip from the handgrip.
In further embodiments, a return-to-neutral spring may be used to operably connect the first control member to the handlebar. In the case of a first control member comprising a thumb lever, for example, the return-to-neutral operation would predictably return the thumb lever to the same home position after each shift operation.
In further embodiments, a spring operably connecting the release member and the takeup element permits the release member to load the spring just prior to releasing the takeup thereby boosting the unwinding operation of the takeup for more positive shifts. Such a spring is described as spring element 10 in U.S. Pat. No. 6,367,347 B1 (Blaschke), assigned to the applicant of this invention, and is fully incorporated herein by reference. In Blaschke, spring element 10 is shown as a coil spring loaded in compression during cable release, but may take on other forms.
In further embodiments, the first control member may be configured to both wind and unwind the takeup element, providing secondary or parallel means for releasing the cable in addition to actuation of the second control member.
In yet further embodiments, the first control member may be configured to rotate solely in the cable pull direction using a ratchet coupling the first control member to the handlebar.
These and other features and advantages of the invention will be more fully understood from the following description of certain specific embodiments of the invention taken together with the accompanying drawings.